Microscale Numerical Simulation of Non-Darcy Flow of Coalbed Methane

Wang, Gang; Yang, Xinxiang; Chu, Xiangyu; Shen, Junnan; Jiang, Chenghao

doi:10.1007/s13369-017-2802-x

Cited by 15 publications

(7 citation statements)

References 21 publications

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“…Currently, the porosity is normally used as criteria to determine the threshold for coal images [41], and this is normally completed through an iterative process to select the threshold for matching the pre-measured core scale porosity, while this approach could be problematic when there is uncertainty of the pre-measured porosity, for example the coal sample may be deformed during measurement under high pressure [42].…”

Section: Binarizationmentioning

confidence: 99%

“…This method was initially adopted by Taud, et al [44] to estimate the threshold of the micro-CT rock image for porosity calculation. And recently, the DTM method was used successfully for determining the threshold value of coal sample [41]. The algorithm of DTM threshold segmentation method has been described in detail previously [44].…”

Section: Binarizationmentioning

confidence: 99%

“…The algorithm of DTM threshold segmentation method has been described in detail previously [44]. For any CT image, the relationship estimated porosity ϕ(x) to its corresponding gray value x can be obtained [41]. The essence of calculating surface porosity of an image is to find the minimum of the function ϕ(x), then the threshold is said to be the grey value corresponds to the minimum of the function ϕ(x) [44].…”

Section: Binarizationmentioning

confidence: 99%

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Imaged based fractal characterization of micro-fracture structure in coal

Zhou

Yao

et al. 2019

Fuel

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To better understand the fractal characteristics of coal fracture network and find the relation between 2D and 3D fractal dimensions, we utilized the improved box counting method to calculate 2D and 3D fractal dimensions based on high resolution CT images of 4 coal samples (Ro from 2.915% to 4.69%). Based on the calculated 2D and 3D fractal dimension and porosity, the size of representative element volume (REV), the relationship between Df2 and Df3 and the relationship between porosity and fractal dimension are investigated extensively. It is noticed that the fractal dimension-based REV of coal is smaller than the porosity-based REV. As the complement of previous theoretical studies, it is proved that porosity has an exponential relationship with fractal dimension. By deducing formulas based on fractal theory, a new way to get the lower self-similar region size from relation between porosity and fractal dimension is provided. Evidently, the relation between 2D and 3D fractal dimension of coal could be expressed as Df3=CDf2+ φ, and the slope of the line, C, depends on the average 2D fractal dimension of the sample. Finally, the reference of the relation between Df2 and C of high rank coal is provided as C=-0.75Df2 +2.75.

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Section: Binarizationmentioning

confidence: 99%

Section: Binarizationmentioning

confidence: 99%

Section: Binarizationmentioning

confidence: 99%

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Imaged based fractal characterization of micro-fracture structure in coal

Zhou

Yao

et al. 2019

Fuel

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“…Pore-scale simulation of non-Darcy flow in porous rock has been made possible as a result of improvements in computed tomography technology. After a pore structure model is constructed through image processing and mesh generation, non-Darcy flow behavior can be implemented by various numerical methods (Bird et al, 2014;Muljadi et al, 2016;Wang et al, 2018;Zhao et al, 2018). Some research in this field has considered the impact of fluid properties on the non-Darcy coefficient.…”

Section: Evaluation Of the Non-darcy Coefficient In The Forchheimer Ementioning

confidence: 99%

Estimation of the Non‐Darcy Coefficient Using Supercritical CO₂ and Various Sandstones

Choi

Song

2019

JGR Solid Earth

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Non-Darcy flow (also known as high-velocity flow, inertial flow, etc.) often occurs in the near-well region of a reservoir during injection or production. This flow needs to be characterized and its origins fully understood, as it is a critical factor in reducing well productivity. The Forchheimer equation, which describes fluid flow considering an inertial effect, can be adopted to analyze non-Darcy flow. In particular, the non-Darcy coefficient in the equation represents inertial resistance in a porous medium and is an empirical value that depends on the pore geometry and fluid properties. This study, as part of research on geological CO 2 storage, reports non-Darcy flow tests with a high flow rate and examines the non-Darcy coefficient by using supercritical CO 2 and various sandstones. The dependence of the coefficient on the properties of the supercritical CO 2 was also assessed in a series of non-Darcy tests under different pore pressures. The coefficient varied with the properties of the supercritical CO 2 and sandstone. As the permeability of sandstone increased, the non-Darcy coefficient decreased nonlinearly and converged to a value. The results also indicate that the coefficient is reduced with a decreasing ratio of density to viscosity for the supercritical CO 2 . An equation predicting the coefficient was derived, having the advantage that both the hydraulic properties of rock and the fluid properties can be considered simultaneously in a dimensionally correct analysis.

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“…Sun et al [28] investigated a fully coupled semi-analytical model for effective gas/water phase permeability during CBM production. To obtain the real physical model characterizing the pore structure of coal rocks and further explore the rules governing the flow of coalbed methane (CBM) using numerical simulation [29]. Wang et al [30] investigated the effect of in situ stress and joint on permeability of the coal bed in Linfen Block, China.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on permeability characteristics of gas-containing raw coal under different stress conditions

et al. 2018

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The present experimental study on permeability characteristics for raw coal under different stress states is implemented by applying the triaxial self-made ‘THM coupled with servo-controlled seepage apparatus for gas-containing coal’; the result indicates that the flow rate of gas in the coal sample gradually decreases with the nonlinear loading of axial pressure and increases with the nonlinear unloading of axial stress and confining pressure. The flow rate, axial stress and confining pressure curves all satisfy the negative exponential function relation. When the sample reaches the peak intensity, the sample will be destroyed and the stress will drop rapidly; then the flow rate of the sample will increase rapidly. At this stage, the flow rate and axial strain show an oblique ‘v' pattern. The flow rate of the coal sample increases nonlinearly with the increase of gas pressure; the relation curve between flow rate and gas pressure satisfies the power function relation. Under the same confining pressure and gas pressure conditions, the larger the axial stress, the smaller the flow rate of the coal sample. Under the same axial stress and gas pressure conditions, the flow rate of the coal sample will first decrease, but then increase as the confining pressure decreases. During the post-peak loading and unloading process, the flow rate of the coal sample will decrease with the loading of confining pressure but increase with the unloading of confining pressure, and there will be an increase in wave shape with the increase in axial strain. The flow rate of each loading and unloading confining pressure is higher than that of the previous loading and unloading confining pressure. At the post-peak stage, the relation curve between the flow rate of the coal sample and the confining pressure satisfies the power function relation in the process of loading and unloading confining pressure.

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Microscale Numerical Simulation of Non-Darcy Flow of Coalbed Methane

Cited by 15 publications

References 21 publications

Imaged based fractal characterization of micro-fracture structure in coal

Imaged based fractal characterization of micro-fracture structure in coal

Estimation of the Non‐Darcy Coefficient Using Supercritical CO₂ and Various Sandstones

Experimental study on permeability characteristics of gas-containing raw coal under different stress conditions

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Microscale Numerical Simulation of Non-Darcy Flow of Coalbed Methane

Cited by 15 publications

References 21 publications

Imaged based fractal characterization of micro-fracture structure in coal

Imaged based fractal characterization of micro-fracture structure in coal

Estimation of the Non‐Darcy Coefficient Using Supercritical CO2 and Various Sandstones

Experimental study on permeability characteristics of gas-containing raw coal under different stress conditions

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Estimation of the Non‐Darcy Coefficient Using Supercritical CO₂ and Various Sandstones